The present invention relates to a heat-shrinkable polypropylene film.
Heretofore, as heat shrinkable films of polypropylene type, there have been widely used biaxially stretched polypropylene films, which are equally biaxially stretched and which have substantially the same heat shrinkability in both longitudinal and transverse directions. The films of this type are suitable for shrink-wrapping an object such as a fast food entirely. However, they are not suitable for use in a case where the shrinkage in one direction is required, as in the case of shrink-wrapping of e.g. a cylindrical bottle.
For this purpose, there has been proposed an unbalance stretched polypropylene film which is stretched primarily in one direction, as disclosed in e.g. Japanese Unexamined Patent Publication No. 77533/1982.
When heated, such an unbalance stretched polypropylene film shows a great shrinkage in the direction of the stretching, but its physical properties such as the tensile strength, are unbalanced as between the longitudinal and transverse directions, with poor physical properties in the direction perpendicular to the stretching direction. Therefore, it has a difficulty such that even when it is used to cover a glass bottle, it does not provide adequate effectiveness to prevent the scattering of the glass bottle fragments when the bottle is broken.